Basically what I have planned for one of mine too.....
Thing to remember with the Getrag boxes is that the number is the theoretical "safe" amount of torque they can handle, so you'd be better off with a Getrag 250 over a 220. Having said that, I had a 220 in my 328i sedan (small mods, nothing super serious) and it withstood the abuse I gave it. Weak point was the M4X clutch which would occasionally slip.
For a daily driver with the occasional abuse, the Getrag 250 box should be more than enough, gear ratios almost identical to the ZF, and they came factory in some E36's (I've pulled one from an early 325i, and there's one in my 316Ti). Clutch/flywheel combo I'll leave up to you as there's a stack out there that can be made to work, the only other thing to think about is your starter may actually need changed to suit the flywheel, and you'll want to swap to a manual diff ratio - assuming it's not a track car that is.